Retroreflective cube-corner sheeting is commonly employed for various decorative and safety purposes. Cube-corner sheeting is often preferred for such uses as traffic signs, pavement markings, vehicle markings and personal safety articles, in view of its high retroreflected brightness. Since its inception, various improvements have been made, such as described by the patent literature that relates to cube-corner retroreflective sheeting.
More recently for example, U.S. Pat. No. 6,206,525 teaches retroreflective sheeting for forming orientation free cones of reflected light encompassing a 0.5 degree angle of observation formed of small metal backed cube-corner prisms in an array in which the size of the prisms are in a range between 0.0005 inch to 0.003 inches on center. The array is formed by casting transparent plastic prisms in a mold formed by ruling three sets of grooves, which intersect at an angle. The grooves are spaced apart in the range of 0.0005 inch to 0.003 inches on center. Before or after formation, the prisms are coated with a reflective material such as a metal. The main disadvantage of very small prisms is described as being that it is very difficult to rule an array of 0.002″ on center prisms over a large area, as the ruling cutting diamond wears out. However, very small prisms are described as having advantages as well, including increased flexibility.